Method of making brake shoes



Oct. 2o, 1925 M. R. DE FRANCE METHOD 0F MAKING BRAKE SHOES original Filed Nov. 1o.--1924 ,EFILLR NVE'N 'FR M Uwe?) RDQ fromme by @fw/m /Lis @Wow-f mi Patented Oct. 20, 1925.

UNITED STATES MURRELL DE FRANCE, 0F BELLEVUE, PENNSYLVANIA. y

mnrnon or MAKING BRAKE sHoEs.

Original application led November l'o all whom t may concern:

.Be it known that I, MURRELL R. DE

lFRANCE, a citizen of the United States',

residing at Bellevue, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in a Methodof Making Brake Shoes, of which the following is a specification.

This invention vrelates to a method of making a pressedmetal and composition brake shoe for use on railway cars and simi. lar vehicles, and to a method of making a' filling block constituting an element of such brake shoe; thisapplication constituting a division of application Serial No. 748,863, filed November 10, 1924.

For a long time previous to the present invention a Wide variety of substances have been utilized in filling compositions for brake shoes. Among such substances may be noted fibrous asbestos, coke, cement, iron y borings, iron ore, plaster, plumbago, resin, sand, sawdust, Wood, and other vegetable fibers. Various oxidizingvegetable oil and various gums have been used as a binderfor these. dry ingredients.' When plaster or cement has been used as an ingredient of the composition, water has been added to set and harden the composition as a Whole.

Brake shoes of the, general type4 mentioned, that is brake shoes comprising a shell of pressed metal and a filling of a l composition formed of various ingredients,

present certain advantages over the cast metal brake shoes commonly in use. Such advantages reside chiefly in manufacturing economy, which is so great that composition brake shoes would largely displace cast metal shoes if the former performed u`nder all conditions of use in as satisfactory a manner as the cast shoe.

It may be stated in connection With cast iron shoes, that the wear on the face of a cast iron brake shoe is by granulation. Under given pressure and load the friction produced by this shoe on a Wheel increases in proportion to the square of pressure until the temperature of the shoe is that of a dull red heat, at which point the friction decreases in direct proportion to the further heat generated. It is to be understood, of course, that under an excessive pressure such as is produced by a stuck brake, a cast metal shoe, or anyv other brake shoe, would be burned up.

10, 1924, Serial No. 748,863. Divided and this application led April 21, 1925. Serial No. 24,737.

The Wearing away of a composition brake shoe .is by pulverization as contrasted'with granulation.v The Wear of the-composition shoe being by pulverization, the shoe and wheel in time becomes so highly polished that the contact between the two is almost perfect. When this condition is produced, an excessive friction greater than that specified for the purposel for which the shoe is used is developed. It will be understood that this `perfect contact and excessive friction is a condition which is not possible with a brake shoe which wears `away by granulation.

It should be understood, also, that the compositions which constitute the filling mal terial for pressedv shell andI composition brake shoes, are very poor conductors of heat. This fact avoids `limitation of the friction developed by the shoe, as is the case when ya cast metal shoereaclies a` red heat i Previous failure of composition brake shoes to compete successfully with cast metal shoes may be traced to three defects, which had to be overcome in order to render them satisfactory under all conditions of use. as

ythe cast s'hoe. The first problem `was to Vprovide a suitable shell, which would not injure-the tread of the wheel to which the brake was applied. This defecthas been graduallyv eliminated by experiment and invention. The second problem'was the development ofY a filling composition which Would carry the crushing load of braking a Wheel independently of the shell in which the composition is carried. This problem is inherently connected with the first, as its solutionwas necessary in order to secure a shell which would not injure the tread of a AWheel. It has also been successfully solved. The third problem has been 'the development of a composition filling which would conform to the specifications of railroads for requisite friction and life, and Which would also approximate the functioning of a cast metal shoev under all conditions of service and at all times during the life of the shoe.

It is this latter problem which has hitherto remained unsolved, and which at the present time limits the use of composition brake shoes. The disadvantages which must be overcome are those of avvearing by pulfverization' to result in perfect contact between the brake shoe and wheel with a far beyond the proper specifications. vconducting such work the inventor herein resultant development of friction in excess `of that specified. For this reason the use of composition brake shoes has been limited to freight cars only. For if a composition shoe be placed on passenger cars, it will be found that the heat generated by excessive friction will be beyond the factor of safety in the operation of trains, and that serious injury tothe treads of the wheels on such trains will be produced.

The manufacturers of composition brake shoes have been aware of this defect, and .its`

has made and tested composition brake shoes in which the coeiiicient of friction increased as greatly as thirty per cent during the life of the shoe. Compositions in whichl the coefficient friction did not increase with use of the shoe varied from an insufficient initial friction to substantially no effective initial friction whatever. y

The general object yof the invention is,

therefore, to provide a method of making a composition filler of such nature that it may be used in a pressed metal shell to form a composition brake shoe capable of approximating the effect of a cast metal brake shoe under all conditions of use` and throughout the entire life of the shoe. i

One specific object of the invention is to provide a method of compat-ting in a single integral block of filling composition areas or strata of different grades of composition, which have different coefficients of friction.

Another object of the invention is to provide a method of compacting in a single integral block of filling composition areas or strata of different grades of composition, which wear aw-ay at different rates during the useful life of the brake shoe.

In the accompanying drawings Figurel is a vertical sectional view through a mold and brake shoe shell, illustrating o-ne step in making a brake shoe by compacting a composition filler into the shell according to the present invention; Figure 2 is al cross sectional view on the line 2 2 Figure l; Figure 3 isa view similar to Figure 1, -but illustrating a more advanced step in conducting the method; Figure 4 is a cross sectional view on the line 4 4 Figure 3; Figure 5 is a bottom plan view of a brake shoe made according to the method of the present invention; Figure 6 is a cross sectional View on the line 6 6 Figure 5; Figure 7 is a vertical sec tional view through the brake shoe shown in Figures 5 and 6 illustrating the condition of the brake shoe after it has been partially worn away in use; andFigure 8 is a cross sectional view on the line 8 8 Figure 7.

In conducting the process of the present invention, a brake shoe shell l, of pressed metal, is laid in Ia mold 2 in the position shown in Figures l to 4 of the drawings. Filling composition in a plastic and readily coinpressible condition` is then introduced into the brake shoe shell and the mold, so that the depth of composition is greater than the depth of shell, as shown in Figure 1. As shown in the drawings,- composition of two different grades is used to form the filling disarranging the layers of the different grades of composition. This is, however, in general unnecessary.

As the strata 3 and 4 of the finished block lie horizontally, and as the working face 5 of the block is concave on an arc of relatively great curvature, the pressing operation results in exposing more than one stratum on the working face of the brake shoe. Due to these factors, moreover. lnore than one stratlnn or area will be exposed on the working face as thel filling block wears away, and throughout the entire-life of the brake shoe.

Horizontal stratification of the different grades of composition in the integral block presents an advantage in simplicity or manufacture over the generally similar form, in which the areas, or strata, are vertically arranged.

It should be noted that the brake shoe- Maryam of the filling block. In order to effect the objects of the invention, these formulae must be such that different areas having at least two different coeicients of friction are provided on the working face of the filling block not only initially but during the entire life of the brake shoe, as the block is worn away in use. lt is also highly desirable that the material in one set of areas should tend to be worn away more rapidly than the material in the other set ot areas. This is eiected in practice by having one or more areas or sets of areas comprise material which tends to pulverization with great rapidity. This effect causes the working face of the block to be constantly covered with loose material, thus preventing perfect contact between the wheel andthe area or areas which are less susceptible to disintegration. lt'is alsoV desirable that a cerltam. ingredient, or certain ingredients, of

such area or areas be such as to cause the loose material to be as coarse as possible, thus approximating the effect of a cast metal brake shoe during its wear by granulation.

Desirable formulae for the different grades of composition are given in copending application Serial No. 748,863, filed November 10, 1924, of which the present is a divisional application. In conducting the method thervarious areas of plastic composition, which are to be compacted into a single integral block, may comprise compositions as disclosed in these formulae, or-any other composition which will produce satisfactory results in use. It is of course a prerequisite that the composition be compressible while in a plastic condition and that it may be hardened, by exposure to air or by baking, into the desired m-tegral block.

It should also be understood that 'the method of the present invention produces no novel advantage in the completed brake shoe, unless the integral filling block produced is composed of two or more grades of composition which have different characteristics. The Iinal block should thus comprise two or more grades of composition which vary either in their coeiiicients of friction, or in their rate of disintegration,

-or in their inherentl tendency to become pulverized in use, or in any two or all of these characteristics. It is to be noted that while the process shows the method as conducted with only two grades of composition, no change in the conduct of the method is necessary in order to incorporate three or. more derent grades in a single lilling block,

it should be further understood that composition illing blocks for pressed metal shells may be made by pressing the bodies ot dilerent grades ci' composition in a mold apart from the shell. This block may be then separately baked, and the metal shell folded and pressed around the integral block 'ol filling composition.

What l claim is:

1. The method of making a composition brake shoe which -consists in positioning a pressed metal shell within a mold, introducing into the shell and mold a plurality of grades of filling composition while in a plastic condition in such manner that the several grades ot filling composition form horizontal strata, and pressing the body of compositionto compact the same into a single integral block.

2. The method of making a composition filling block for use in the pressed metal shell of a composition brake shoe which consists in introducing into a mold a plurality of grades of filling composition while in a plastic condition Vinsuch manner that the several grades of fillingcompositlon form horizontal strata, and pressing the body of composition to compact the same into a single integral block.

1n witness whereof, I hereunto set my hand..

MURRELL R. DE FRANCE.` 

